A proper and detailed understanding of the thermal stability of Fe-rich fayalite slag-based alkali-activated materials (AAMs) is important due to their potential use in refractory and fire-resistant applications. Here, fayalite slag (FS) was used as the main precursor for AAMs. The effects of incorporating ladle slag (LS) or blast furnace slag (BFS) and different temperature exposures up to 1000 °C were investigated through visual observation, compressive strength, ultrasonic pulse velocity (UPV), thermal conductivity, x-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope coupled with electron probe microanalyzer (SEM-EPMA). The experimental results indicated that the incorporation of LS or BFS as additional calcium and aluminum sources positively affected the high-temperature behavior of blended mortars, which exhibited a reduction in voids, cracks, and thermal shrinkage while having higher residual strength and thermal stability than solely FS-based AAMs. This was mainly due to the differences in mineralogical transformation and the phases formed. Interestingly, the joint effect of elevated temperature exposure and the addition of LS or BFS enhanced the formation of more stable crystalline phases and densified the structure of blended mortars at 1000 °C. Display omitted •Upcycling of Fe-rich fayalite slag as refractory and fire-resistant alkali-activated materials (AAMs) was elucidated.•Ladle slag (LS) or blast furnace slag (BFS) addition improved AAMs properties during ambient and high temperature exposure.•AAMs containing LS or BFS have better mechanical, thermal, and microstructural properties.•Joint effect of elevated temperature and LS or BFS addition favored more stable crystalline phase formation and densification.•The results provided an insight for designing eco-friendly refractory materials for building and construction industry.